Annealing box



May 11, 1937. B@ R, SWT... 2,080,014'

ANNEALING BOX Filed Feb. 25, 1936 2 Sheets-Sheet 1 Zzzrd Feed 512712122 @may May 11, 1937. B. R. SMITH 2,080,014

ANNEALING BOX Filed Feb. 25, 1936 2 Sheets-Sheet 2 gmc/YM Patented May 1l, 1937 PATENT OFFICE ANNEALING BOX Burd Reed Smith, Sharon, Pa., assignor to The Petroleum Iron Works Company of Ohio, Sharon, Pa., a corporation of Ohio Application February 25, 1936, Serial No. 65,693

9 Claims.

l The principal object is to prolong the useful life of annealing boxes by so constructing them as to obviate conditions or nullify forces tending to destructive deformation.

The normal life of an annealing box is measured by its ability to resist scaling and by its ability to withstand distortion. Scaling is no particular problem and successfully can be controlled by constructing the annealing box in whole or in part of suitable alloy metal, such as, for example, chrome steel. Distortion is a decided problem notwithstanding that the cause and effect are apparent. The proposition succinctly may be stated as follows:

If heat is applied to one side of a flat plate, it will take a bow, `or arch, or spherical shape, with the center of curvature on the side of the plate opposite the heat. If cold is applied, a similar effect is observed, except that the center of curvature is on the side to which the cold is applied. This can be readily demonstrated with a celluloid triangle.

4If a steel plate', free to expand, is heated from one side to a temperature below about 800 Fahrenheit, on cooling, it will return to its original shape. The same is true of chilling from one side. In heating an annealing box, it is placed in an oven at from l200 to 1800* temperature. This heat will strike the outside of the box. The inside will have the pack of cold metal and will heat slowly. Assuming the sides, top and ends to be flat, each surface will become dome-shaped, with a radius toward the inside of the box. This will be an elastic deformation until at some time the outside reaches a temperature of about 800 when the strains will cause creep. If the annealing box were then removed from the oven and allowed to cool from both sides, there would be a permanent set on each face with the center of curvature on the inward side of the face, but this is not the case because the cover is left on the pack of hot metal when it is taken from the furnace into the cold air, and the inside of the box is kept hot while the outside is chilled; also, the inside of the plate is hot enough to creep after the outside is below that temperature. Consequently, the dome reverses itself so that the radius of curvature is on the outside.

Due to the outward creep on rst heating and the inward creep on cooling, it results that when the box is cold, each face tends to dish inwardly. This dishing result will not be uniform because the amount of dishing in the top will be increased by the weight of the top, and as the box is an integral structure, thedeformation of the top afiectsthe sides and ends, and vice versa. This inward dishing is what must be counteracted because it reduces the inside dimensions of the box, and consequently reduces the quantity of steel that can be heat-treated. The deformation is especially bad on the top, because it is aggravated by the weight of the sagging metal.

It has been common practice to dish the sides and top convex to the outside. This, in most cases, is satisfactory for sides and ends. Often the ends of the box are left flat. The amount of the original dish varies with the oven design and heat-treatment. Generally, the dish on sides and ends does not extend over the entire plate, a spherical embossment being pressed in the center of the` flat side covering about one quarter of the plate. Distortion oi the sides and ends can be thus controlled, and it is common practice so to do. The same satisfactory results have not been obtained by dishing the top, although the area pressed is much larger.

I have discovered that the problem can be solved and destructive deformation prevented by relieving the stresses in the roof or' tcp which result in inward dishing and eventual permanent set, and this I do by providing the regular or normal outwardly directed dished area of the top with an outwardly directed secondary dish which functions as an expansion joint during the heating and cooling of the top, so that the tendency to dish inwardly and take a permanent set is much lessened, if not entirely obviated, and the life of the box is greatly prolonged.

The nature, characteristic features and scope of the invention more readily will be understood from the following detailed description taken in connection with the accompanying drawings, forming a part hereof, wherein Figures 1, 2 and 3 are, respectively, side, top and sectional views of one iorm of the invention, the section being taken on line 3-3 of Figure 1.

Figures 4, 5, and 6 are, respectively, side, top and sectional views of another form of the invention, `the section being taken on line 6-6 of Figure 4.

In the practice of the invention the side plates and end plates 6 may be as usual and both sets of plates may be dished in the conventional or any suitable way. Preferably, I leave the end plates flat and simply dish the side plates by out- Wardly pressing them on spherical lines, as` at l. The side and end plates are assembled and secured in any suitable way and preferably by joining their meeting edges by electric fusion welding as best calculated to overcome failure at the joints.

For relatively long and narrow boxes, as shown in Figs. 1, 2, and 3, the top plate or roof 8 is pressed or otherwise formed to provide an outwardly convexed or dished portion characterized by a pronounced flat arc 9. According to the invention and for the purpose and with the result of counteracting in' service the natural tendency of the dish to collapse or take a position below the top edges of the side walls, I provide it with means that acts as an expansion joint during the heating and cooling periods. In this form of top such means is defined as an elliptical bilge or corrugation l@ outwardly pressed along the longitudinal center line of the dish and having its maximum width and depth at the center thereof.

On boxes more nearly square, as in Figs. 4, 5, and 6, the cover plate I i is formed with a regular crown or dish E2. This in turn is centrally provided with a small dome or bulge I3 which acts as an expansion joint during heating and cooling to prevent or materially lessen inward dishing of the cover plate.

The cover plates are also preferably secured by electric fusion welding and after the assembly is completed, the boxes are annealed.

Having described the invention, what is claimed as new is:-

l. An annealing box having a normally outwardly dished top plate, the dish having an outward bilge formed wholly within the marginal limits thereof effective in service as an expansion joint to relieve conditions tending to collapse of the top.

2. An annealing box comprising end plates and reversely dished side plates, and an outwardly dished top plate, said plates being joined at their meeting edges by electric fusion Welding, the dish of the top plate having an outwardly directed embossment effective as an expansion joint.

3. An annealing box comprising side plates, end plates and an outwardly dished top plate electrically welded to provide an integralstructure, the dished portion of the top plate having a secondary dish characterized by a central bilge outwardly convexed and which functions as an expansion joint during heating and cooling.

4. An annealing box having a head formed with outwardly directed primary and secondary dished portions, both Within the confines of the head and directed in common along the larger dimension thereof.

5. An annealing box having a wall formed with an outwardly directed primary dish portion, and a secondary dish portion Within the bounding limits of the primary dish portion and extending outwardly and beyond said primary dish portion, for the purpose and with the result of preventing inward dishing of the Wall in service.

6. .An annealing box having a head formed with an outwardly directed primary dish, and said primary dish having an outwardly directed secondary dish dened as an elliptical bilge ranging longitudinally of the primary dish and having its maximum width and depth at about the center thereof.

7. v.An annealing box having a head formed with an outwardly directed primary dish, said primary dish having an outwardly directed secondary dish, said secondary dish being formed wholly within the marginal limits of the primary dish, and the primary dish being formed on a radius which will insure a relatively low rise.

8. An annealing box having a wall formed with an outwardly directed primary dish portion, and a secondary dish portion within the limits of the primary dish portion and extending outwardly beyond the same.

9. An annealing box having a wall whereof the area is substantially constituted by an outwardly directed primary dish portion, said dish having a relatively at arc, and a secondary dish portion extending beyond the primary dish portion and having a relatively at arc, said primary dish portion having its bounding limits within the area of said wall, and said secondary dish havin-g its bounding limits Within the area of the primary dish.

BURD REED SMITH. 

